With new 4G networks, wireless Web surfing can now be faster than your home connection. But you must still be wary: Get too addicted to high-speed, go-anywhere Internet, and you might rue the day your bill arrives.

Wireless modems and Mi-Fi hotspots can connect more than just laptops to the Web anywhere. Hotspots will work just fine with an iPod touch, an iPad, the new Kindle Fire tablet, or any other device that's Wi-Fi-enabled. They can even turn those devices into phones, with the right voice-over-IP software. Depending on your hardware, plan and usage, nationwide connectivity can start at $10 per month for very occasional use, although prices can run well over $100 if you decide to download a lot of movies and games.

Here's what you need to know to pick the right service and hardware:

First, Understand the LimitsWireless broadband isn't for everyone. If you download a lot of movies or want to use the Internet day-in, day-out, a hotspot or a cell modem probably won't do the trick, you'll likely need a true wired connection. Sprint (also known as Clear) offers the only truly unlimited 4G plan, so it's the only carrier suitable for heavy users, but even there, you're limited to 5 or 10GB/month if you fall back onto Sprint's 3G network. Most 3G networks are also too laggy for gaming and video chat, although Verizon's and AT&T's new 4G LTE networks seriously improve response times.

Hardware TypesThere are two main types of modem: USB sticks and MiFi-style hotspots. Cards that popped into a slot in your laptop used to be popular, but they're going out of style. We've seen very few in the past year.

USB sticks offer the fastest possible connections and are more portable than Wi-Fi hotspots. They're best for use with a single laptop. Typically, you must load special drivers and connection software onto your PC to use a USB stick. Most of the connection software is fine, but Sprint's SmartView is slow and buggy.

Mobile Wi-Fi hotspots such as Novatel's MiFi 4510L and Sierra's Overdrive Pro let you hook up multiple PCs, iPads, iPhones, and other mobile devices to the Internet via Wi-Fi. They're very easy to operate, and you typically don't have to load any special software onto your PC to connect with one. But they give you yet another gadget to charge, and translating a connection from 4G to Wi-Fi can bleed up to 20 percent of the connection's speed.

3G vs. 4GSeveral carriers say they have "4G" networks nowadays, but not all 4G is alike. Generally, you can expect speeds around 1Mbps down on 3G networks, but the "4G" technologies vary much more wildly.

The gold standard of 4G right now is Verizon's LTE network, which currently covers 160 million Americans with average download speeds of around 9Mbps, according to our 21-city Fastest Mobile Networks tests earlier this year. AT&T has just started building a similar LTE network, promising to launch 15 cities covering 70 million people by the end of 2011.

T-Mobile's "4G" is HSPA+ 42, which can achieve average speeds around 8Mbps with the right device. (You need a modem like the new Sonic 4G Hotspot which can match the network's speeds.) Sprint's 4G is WiMAX, a totally different and incompatible technology covering about 120 million people that we found averaged about 3Mbps down. Finally, in most of the country, AT&T advertises a slower variety of 4G, HSPA 14 or HSPA+ 21, which we found averaged 2.44Mbps down in our nationwide tests.

Choose Your CarrierWith so many competing technologies, coverage and price are critical. AT&T has several modems and hotspots, but for the best compatibility with the carrier's future network we recommend getting the LTE-compatible Elevate 4G hotspot or Momentum 4G USB modem. AT&T requires a two-year contract for modems and hotspots, and charges $10 per GB of use with a minimum of 5GB/month.

Cricket covers about a third of the nation with somewhat slow, but reliable 3G. Cricket offers 2.5GB/month for $45, 5GB for $55, and 7.5GB for $65 with no contract. If you go over the max, Cricket won't cut you off, but it will slow you down until the next month starts.

Again, Sprint offers the only truly unlimited 4G plan, so it's the only network you can use as a replacement for a home connection. For $60/month, you can get a 3G/4G modem or hotspot that works on Sprint's WiMax network where that's available, or on 3G where it isn't. That $60 buys you 5GB/month of 3G usage; $80 buys you 10GB. Unfortunately, Sprint's 4G network only covers about a third of the country and it hasn't expanded recently.

For unlimited Sprint 4G with no contract, look to Clear, which has a $45/month unlimited 4G-only, no-contract plan. If you're in a Sprint 3G zone, Sprint's Virgin Mobile brand will sell you 500MB of 3G service for $20 or 2.5GB for $50, prepaid.

T-Mobile recently bumped its HSPA+ network to HSPA+ 42, which the carrier says is almost as fast as LTE. T-Mobile offers 2GB for $40/month, 5GB for $50, or 10GB for $80, and like Cricket, it will throttle speeds rather than cutting you off if you go over your limit. The carrier also has no-contract plans: $30 for 1GB or $50 for 3GB.

Verizon Wireless delivers a Cadillac network for Cadillac prices. Its LTE network covers 160 million people and is the fastest in the land. Since it costs $50/month for 5GB and $80 for 10GB, though, you shouldn't turn off your home cable or DSL line anytime soon.

US Cellular, Cincinnati Bell, and other smaller carriers also offer modem solutions, but we haven't reviewed them.

Can't get coverage where you live? WISPs (wireless ISPs) generally use larger, home-based modems, but they're available in many (though not all) small towns where traditional broadband or cellular service can't be found. What's more, they don't carry 5GB limits.

To Tether Or Not To Tether?If you decide to make the jump, hotspots and cellular modems aren't the only option. You'll find a wide range of laptops and netbooks with integrated 3G or 4G from almost every manufacturer, except Apple. In our tests, these devices typically deliver solid speed and reception—but of course, you've got to buy a new system, and you may be yoked to one wireless carrier for the life of the PC.

Most smartphones, such as Verizon's Motorola Droid Bionic and the Apple iPhone 4 also have integrated "wireless hotspot" modes, which let them connect other devices via Wi-Fi. You have to pay an add-on fee, usually around $20/month, and you'll typically get around 2GB of data use. This is a good solution for occasional use, but since it drains your phone's battery, it isn't an all-the-time solution.

Extras and Bonuses Many modems offer features beyond simple connectivity. Some add GPS functionality to your laptop, which I haven't found all that useful; the GPS radios in modems are less sensitive than those in smartphones, and it's a bit awkward to use your laptop for navigation. A more-useful feature, many modems have connectors for external antennas, which can really boost signal strength in rural areas. The Sierra Overdrive Pro and Elevate hotspots have official signal-boosting docks, while sites like AntennaGear.net sell third-party antennas for other modems.

I also really like the LCD display on the Overdrive Pro and the graduated lights on the Cricket USB Broadband Modem A600, both of which report the strength of your 3G signal right on the device.

Beware: Overseas Surfing Will Cost YouTraveling abroad? Roaming can be insanely expensive, so we generally recommend renting a MiFi from XCom Global instead. XCom's MiFi plan covers several dozen countries including most of Europe and costs $15-18/day for unlimited use, which is much less than you'll pay with a U.S. carrier.

AT&T modems will work almost everywhere in the world, but if you're leaving the country, you should get a temporary data add-on to your service plan. You can opt for from 20MB to 200MB of data usage ($25 to $229 per month). If you don't have one of these plans, you'll be charged up to $20 per megabyte (that's MB, not GB) for data overseas. Ouch. T-Mobile modems also work abroad, but add-on plans are not available—it's just $15 per megabyte outside the U.S. and Canada.

If you're with Verizon, your modem will work in Canada, and the company offers the FiveSpot global hotspot that works with plans starting at $30/month for 50MB. Otherwise, you're stuck with a $20-per-megabyte rate. Sprint also has an international hotspot, but it offers no overseas data-roaming plan; if you go to Europe, for instance, you'll pay a flat rate of $16 per megabyte.

Unlocked world-capable modems do exist, and in theory, you can put a foreign SIM card into an AT&T or T-Mobile modem to get local service at low rates. But in practice, I've found this to be nearly impossible to achieve. Modem and OS settings are so arcane, especially when you're dealing with customer service in a foreign language, that I can't push this as a practical solution.